In crosscutting machines which, by crosscutting a web of material, particularly a paper or cardboard web, produce individual sheets to be subsequently deposited on a stack and which operate at high speeds, it is required to slow down the these sheets transported by belts to the stacking location, prior to stacking, in order to insure that the stacking of the sheets is undisturbed.
From DE-B 20 00 078 a generic method is known, according to which the sheets are guided over a fixed suction chamber provided with holes which in a timed manner slows down the trailing edges of the sheets by suction. Subsequently, the sheets are transported to the stacking location by belts running at a speed appropriate for stacking. Since the following sheet runs at first without being braked, its leading edge slides over the trailing edge of the braked sheet, so that the sheets overlap in a scale pattern and are this way transported further. Since the suction acts in each case only upon the lowermost sheet, in multilayered operations wherein for instance eight webs are simultaneously subjected to crosscutting, it is required to provide additional braking for the pack of sheets. This is done by means of a slower running belt portion inclined with respect to the transport plane, against which the leading edge of the sheets of a pack will push.
The known braking devices are expensive structures. It is also possible that, in the case of particularly sensitive papers, marking can occur due to the relative speed with respect to the braking elements. Furthermore, at high operational speeds, sheet jamming may occur.